Gear Test Rig with Worm-Gear Preload and Torsion Measurement

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Solution Overview

Problem

Existing stress test rigs are complex and imprecise, lacking efficient methods for introducing tension into closed-loop torque circuits and accurately measuring torsion without significant power loss.

Innovation Solution

A stress test stand design featuring a gearbox with a connecting shaft, preload unit, and a hollow shaft, utilizing a self-locking worm gear mechanism to introduce tension and measure torsion accurately, allowing for easy adjustment and detection of torsional forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a connecting shaft is used to connect two first shafts in a rotationally fixed manner, then the torque circuit is closed and torsion can be measured, but the device complexity increases

Engineering Contradiction:
Improvetorsion measurementVSAvoiddevice complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

A hollow shaft is introduced as an intermediary element between the two first shafts. This hollow shaft serves as a mediator that allows torsion measurement while maintaining the closed-loop torque circuit configuration, thereby enabling precise measurement without excessive complexity

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces complex mechanical measurement systems with a simplified hollow shaft configuration that uses optical or sensor-based detection to measure torsion, reducing mechanical complexity while improving measurement precision

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If a preload unit is introduced to apply tension to the closed-loop torque circuit, then torsion can be applied for testing, but the device complexity increases

Engineering Contradiction:
Improvetesting capabilityVSAvoiddevice complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The preload unit is designed with a worm gear mechanism that serves multiple functions: applying preload, maintaining tension in the closed-loop torque circuit, and enabling reversible tension adjustment. This multi-functionality reduces the need for separate components, thereby reducing overall device complexity

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The worm gear mechanism provides self-locking functionality, automatically maintaining the applied preload without requiring continuous external actuation. This self-service capability simplifies the control system and reduces device complexity while maintaining testing versatility

Inventive Principle:
Principle #25Self-service

3Reliability

If a worm gear mechanism is used to introduce tension, then the tension can be reliably maintained, but power loss occurs

Engineering Contradiction:
Improvetension maintenanceVSAvoidpower loss
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The patent optimizes the worm gear parameters (helix angle, gear ratio) to minimize power loss while maintaining self-locking functionality. By carefully selecting these parameters, the system achieves reliable tension maintenance with reduced energy loss

Inventive Principle:
Principle #35Parameter changes

4Ease of operation

If the connecting shaft has a small cross-section to make torsion visible, then torsion detection is simplified, but the shaft strength is reduced

Engineering Contradiction:
Improvetorsion detectionVSAvoidshaft strength
Core Design Contradiction:
Ease of operationVSStrength

Solution Approach 1:

The patent replaces the visual detection method with sensor-based detection systems that can measure torsion in the connecting shaft without requiring the shaft to have a visibly large deformation. This allows the shaft to maintain adequate strength while enabling precise torsion measurement

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The hollow shaft configuration allows optical detection methods to measure torsion by detecting changes in the shaft's geometry or position, eliminating the need for large visual deformations and allowing the shaft to maintain optimal strength dimensions

Inventive Principle:
Principle #32Color changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables precise and efficient introduction of tension into closed-loop torque circuits with minimal power loss, facilitating easy adjustment and accurate measurement of torsional forces.

Implementation Method 1

a worm gear (30) is non-rotatably connected to the preload sleeve (21)... Two rotatably mounted worms (31)... in engagement with the teeth of the worm wheel (30)

Methodology Applied
Scientific EffectWorm gear mechanism: Worm Drive

Implementation Method 2

the worm gear (30) is formed from each worm and worm wheel is self-locking, particularly in that the helix angle of the worm's teeth is so small that the worm acts as a self-locking mechanism against the worm wheel

Methodology Applied
Scientific EffectSelf-locking mechanism: Ratchet

Implementation Method 3

a hollow shaft (5), in particular a measuring shaft, projects wholly or at least partially beyond the connecting shaft (6) in the axial direction... the rotation of the connecting shaft relative to the hollow shaft (5) is easily detectable

Methodology Applied
Scientific EffectTorsion measurement: Deformation

Data Source

PatentEP4370891B1Gear test rig having transmissions and an electric motor
Publication Date: 2026.04.01 SEW EURODRIVE GMBH & CO KG
  • EP4370891B1 patent drawingFigure 1
  • EP4370891B1 patent drawingFigure 2
  • EP4370891B1 patent drawingFigure 3

AI summary

A gear test rig, having transmissions and an electric motor, wherein each transmission has a first, in particular input, shaft and a second, in particular output, shaft, wherein a connecting shaft, in particular torsion shaft, connects two of the first shafts to each other for conjoint rotation, in particular wherein a respective clutch is arranged between the connecting shaft and the respective first shaft, wherein two of the second shafts are connected via at least one pretensioning unit.